It is known that integrated circuit (IC) thermal enhancement is a requirement for advanced development in electronic packaging. The current cost effective means to enhance the thermal performance of die-up plastic ball grid array (PBGA) packages are:
(i) to include power and ground planes in the laminated substrate; and
(ii) to incorporate thermal vias and thermal balls below the die area in the laminated substrate
If the above means are not able to lessen the die operating temperature of the PBGA packages in the required specification, cavity-down thermally enhanced ball grid array (EBGA) packages are generally adopted to meet the more stringent thermal requirements. However, the cost of the current EBGA packages is much higher than die-up laminated PBGA packages.
U.S. Pat. No. 5,977,626 to Wang et al. describes a PBGA semiconductor package having a heat spreader placed on the substrate and over the die by a pick and place apparatus. The molding compound is then formed over the die. The package is turned upside down and solder balls are implanted on the surface of the substrate.
U.S. Pat. No. 5,949,137 to Domadia et al. describes a flip chip packaging assembly having a stiffener device formed from a single stamping or punching operation to maintain a substantially planar upper and lower surface. The stiffener device includes a heat spreader positioned atop the flip chip device.
U.S. Pat. No. 6,011,304 to Mertol describes a heat spreader for a cavity down ball grid array (BGA).
Accordingly, it is an object of the present invention to provide an improved method of forming an exposed drop-in heat spreader PBGA package.
Another object of the present invention is to provide an improved method of forming an embedded drop-in heat spreader PBGA package.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a mold chase for a PBGA package is provided. The mold chase has an open side with and exposed bottom wall and side walls, and a bottom side. The mold chase is positioned open side up. A heat spreader is dropped into the mold chase open side. The heat spreader has a lower protruding section, and lateral peripheral flanges with gaps therebetween. The protruding section contacts a portion of the bottom wall of the mold chase and the flanges contact a portion of the exposed side walls of the mold chase to thereby secure the heat spreader within the mold chase. A flowable molding compound is applied over the heat spreader to completely fill the space above the heat spreader. The flowable molding compound also flows through the heat spreader peripheral flange gaps into the space below the heat spreader flanges, completely filling the lower space. A substrate, having a die affixed thereto in a die down position, is fixedly placed over the molding compound filled mold chase. The die being positioned within the space above the protruding section of the heat spreader. The molding compound is cured to form a die-up laminated PBGA package.